Flow cytometers are use in research and clinical applications to analyze the characteristics particles or cells. Typically, in these systems, a particle stream is injected into the center of a laminar sheath flow stream. The combined stream is passed through an interrogation region, where cells of interest are identified. In droplet sorters, the stream may subsequently be divided into droplets, with droplets containing the cells of interest be sorted into separate collection chambers.
A sheath flow delivery system should provide sufficient flow capacity with a substantially invariant flow rate and pressure. The stability of the flow is especially important for sorting applications, because variations in the flow affect the ability of the sorter to efficiently and effectively sort. Additionally, sheath flow delivery systems should provide sheath flow free of bubbles, maintain the sterility of the sheath flow and allow for the replacement of the sheath flow container or reservoir during a sorting operation.
Even further, sheath flow delivery systems should provide stable sheath flow in the presence of variations in the operating environment (e.g., temperature, etc.), variations in the equipment operation (e.g., run-in, voltages, etc.), and variations in the fluid flowing through the system (e.g., pressures, viscosity, etc.).
U.S. Pat. No. 8,597,573 to Gilligan (issued Dec. 3, 2013), which discloses a continuously regulated precision pressure fluid delivery system, is hereby incorporated by reference in its entirety herein. Gilligan discloses a fluid flow characteristic regulator which provides a variable volume flow path in which a fluid flow can be continuously adjusted by a control fluid to regulate at least one fluid flow characteristic of the fluid flow within the variable volume flow path.